Private automobiles represent one of the largest single classes of energy consumers in the United States. A significant portion of fuel consumption of automobiles is due to the growing use of air conditioners. Additionally, air conditioning equipment constitutes a significant fraction of the initial cost of the private automobile. Such equipment typically is provided with a reciprocating piston compressor which is mechanically coupled to the engine and is generally complete in itself as an add-on component.
On the other hand, waste heat from automobile engines is available virtually free of cost and is responsive to relatively high energy level uses. Within minutes, even at idle, tail pipe temperatures exceed 500.degree. F. Fully 40% of the heating value of total fuel consumption of a spark ignition engine exits at the tail pipe. Another 35 to 40% leaves by the cooling system. At cruising conditions, gas temperatures exceeding 1200.degree. F. are produced. Such high temperature conditions result in the formation of environmentally burdensome amounts of oxides of nitrogen.
Accordingly, it would be desirable to provide some means of high rate utilization of the exhaust heat to take economic advantage thereof and to reduce the rate of formation and concentration of emissions of oxides of nitrogen. The present invention provides a means for effectively and economically controlling engine temperatures while utilizing the otherwise wasted heat generated by an automotive engine, thereby reducing the overall temperature of the system. In particular, the present invention combines an improved automotive engine cooling system with an air conditioning system which utilizes waste heat from the engine to vaporize refrigerant fluid which travels through a condenser and is pumped back to the engine. While the present system uses a smaller than conventional coolant pump which may be either driven by the fan belt or electrically driven, there are no additional high-speed rotary or reciprocating compressor parts such as bearings, belts, dynamic seals, lubricants, clutches, or other mechanical features as presently required for air conditioning. Accordingly, wear and leakage are eliminated as factors limiting the service life of the equipment. Furthermore, as the engine coolant is caused to undergo a liquid-to-vapor phase change in the cooling jackets, high heat transfer rates to the virtually constant temperature organic, inert, dielectric fluid will result in greater uniformity of temperature of engine parts, thereby reducing thermal distortions, corrosion, hot spots, lubricant break-down and, consequently, engine wear. The high-rate heat transfer characteristic should be particularly valuable in high performance and rotary (Wankel) engines, especially when aluminum construction is used.
Specifically, in a cooling mode, vaporized refrigerant fluid is conveyed via a jet ejector through a condenser/radiator while a portion of the fluid is diverted from the condenser to a conditioner/fan-coil which serves as a refrigerant evaporator. The diverted portion is evaporated at the conditioner to produce a refrigeration effect and is then returned to the condenser by aspiration via the jet ejector. A high degree of efficiency can be accomplished by heat exchange through crossing vapor and liquid lines and by the use of thermostatic controls, as will be described.
In a heating mode, the vaporized refrigerant fluid is conveyed in a reverse direction directly through the conditioner and then to the condenser. In this mode, the conditioner serves as a condenser to provide a heating effect.
Cooling or heating is selected by appropriate valving. When both modes are closed out of the circuit, the pump circulates the refrigerant in a closed loop between the engine and condenser/radiator via a pressure relief by-pass valve which limits the maximum refrigerant, and thus engine jacket, temperature, to the saturation value corresponding to the pressure relief setting. Additionally, a normally open thermostatically controlled valve permits by-pass of the engine to acclerate warm-up on starting. When neither heating nor cooling modes dissipates sufficient heat to maintain proper engine jacket temperatures, the excess refrigerant vapor is automatically by-passed directly to the condenser/radiator which has sufficient capacity to reject all engine jacket waste heat to ambient air.